Coparenting with a narcissistic ex!

Not sure if this is the right place to post. And I don't want to ask on social media for obvious reasons. Anyone know of any good books to hopefully try and deal with coparenting with my ex husband. He's a narcissist and extremely verbally abusive in front of my son. Everything is a fight, we have been in and out of court for the past 3 years. The most recent absurdity is his new girlfriend is now making our 6 year old call her mommy! I've had enough and dealing with him has put a strain on my relationship with my current boyfriend of 2 years. I don't know what to do anymore! Help!!